bxtn

Hi, so I'm a beginner angler currently just using a Shimano rod and reel Sienna combo with 10lb mono for some basic bait fishing but looking to start on some lures. Last week I picked up a Daiwa TD Black Wicked Weasel and a Shimano Sedona 2500FI to start on some soft plastics. My target species are flatties but also hoping to catch some bream too. I was thinking of getting 6lb braid and 10lb fluorocarbon leader but would that be too heavy for catching bream as well? Like I read that heavier lines means you'll get less bites than a lighter line but can anyone explain why? Would I also be able to catch bream at a decent rate while also getting flatties with 10lb fluoro? Thanks.